Installation guide

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Wi-Fi Location-Based Services—Design and Deployment Considerations
OL-11612-01
Deployment Best Practices
Detailed procedures covering the steps involved in performing a RF calibration can be found in the Cisco
Wireless Location Appliance: Deployment Guide at the following URL:
http://www.cisco.com/en/US/products/ps6386/prod_technical_reference09186a008059ce31.html.
Calibration Validity
A properly performed site calibration is considered valid as long as the fundamental environmental
factors affecting RF propagation (such as attenuation, path loss, and so on) in the target environment
have not deviated significantly from the state under which the original calibration was performed. For
example, significant changes in the material contents of the target environment may have impact on the
path losses experienced. Unless accounted for with an updated calibration, such changes may cause
inaccuracies when using calibrations and path loss models that were formulated in the past.
Whenever there are significant changes in factors affecting RF propagation in this manner, calibration
should be repeated. This allows the system to better understand the level of attenuation and fading
present in the current environment and allow it to re-calculate the path loss model. In many cases, this
aids in restoring lost performance to the system under the conditions found in the new environment.
Examples of the types of changes where a re-calibration might be recommended if a significant drop in
performance is noticed include but are not limited to the following cases:
• Changes in material—A storeroom that once contained paper products has been converted to a food
storeroom stocking canned goods (that is, canned peaches in heavy syrup).
• Changes in interior walls—A newly re-modeled hospital now has interior walls and metal swinging
doors installed where none existed before. The composition of some existing walls has changed
from drywall construction to another material to meet new health and safety codes.
• Changes in stocking density—A large storeroom was originally calibrated when racks contained
only six shelves of equipment. But now, density has increased to ten shelves per rack.
• Changes in stocking levels—A large stockroom that was calibrated when it was less than fifteen
percent stocked, but now is filled to capacity.
Keep in mind that not every environmental change requires a re-calibration. Assuming that the original
installation followed recommended best practices, one or more of the following changes occurring
within the environment would normally not necessitate a re-calibration:
• Changes in the number or location of access points installed
• Changes in the type or gain of antennas
• Changes in the compass orientation of antennas
Note Note, however, that the re-positioning of current access points or the addition of new ones will require
the updated network designs to be re-synchronized between WCS and the location appliance.
It has been noticed that in cases where Cisco Aironet 1230 LWAPP access points are deployed in
location-aware designs, inconsistencies in reported client signal strength levels may occur at times.
Therefore, Cisco recommends that when Cisco 1230 Aironet access points are deployed, a site
calibration should always be performed.